1. Field of the Invention
The present invention relates to a rotary actuator having a drive body that is rotated around its rotation axis. More particularly, the invention relates to a technique that is useful when applied to wipers for cars, outdoor monitor cameras, and meters such as speedometers. This invention also relates to a method of controlling an actuator that is driven by the vibration of an electromechanical transducer such as a piezoelectric element. More particularly, the invention relates to a method of controlling an actuator that can reduce the noise the actuator makes when the input voltage changes.
2. Related Art Statement
Hitherto, a rod-shaped member such as a wiper blade is driven to wipe a glass pane, and a rod-shaped member such as the pointer of a meter or a hand of a clock is driven to indicate a numerical value. Generally, wipers, meters and clocks use rotary actuators driven by electromagnetic motors or hydraulic or air pressure. Electromagnetic motors and the like are considerably large. Due to their sizes, their design and installation are limited. For example, it is desired that a small CCD camera be equipped with a wiper to clean the front of the camera, but a wiper with a motor or an actuator cannot be used because it decreases the view field of the camera and occupies a large space. Most conventional drive mechanisms comprising an electromagnetic motor or the like requires a decelerator, a link and the like, besides the electromagnetic motor or the like. Inevitably, the drive mechanism tends to be massive and heavy, and has problems concerning a space and weight. The manufacturing cost of the drive mechanism is high, due to its size and weight.